Pompey’s automatic promotion hopes suffered a dagger blow as they slipped to a depressing 3-0 loss to Newport County.
Darren Jones, Scott Boden and Dean Morgan got the goals at Fratton Park on a poor, poor afternoon for the Blues.
Referee Ben Toner took centre stage as he dismissed Gary Roberts for diving 14 minutes after the restart.
That gave Cook’s side a mountain to climb after Jones’ first-half header put the Exiles in front.
The gap to the top three remains six points as Oxford United and Plymouth both lost.
But that just underlined what a wasted opportunity it was for Paul Cook’s men as they dropped to sixth.
Alex Rodman fired wide for the visitors after two minutes.
Then it was Marc McNulty’s turn to drag his shot wide from 30 yards.
But it was very flat stuff at Fratton Park with the crowd eerily quiet in the spring sunshine.
Pompey were lacking the vim and impetus in their passing so apparent in Tuesday’s win at Accrington.
And Cook showed some frustration at his players choosing to go backwards with their passing.
There was virtually nothing in the way of chances - until the visitors made the breakthrough after 35 minutes.
The goal was a messy one as Medy Elito put a ball into the box and Ryan Fulton went up with Jones.
The defender got his head to the ball to knock it home, and the whistle the keeper was looking for from the ref was not forthcoming.
Joe Day was required to block a shot from Marc McNulty in stoppage time, but that didn’t stop a sprinkling of boos greeting the half-time whistle.
Roberts upped the tempo three minutes after the break with a shot on the turn which Day held.
Boden replied by threading a shot at Fulton which the keeper comfortably dealt with.
Michael Smith, who was introduced at the break, then header at Day from 12 yards from a corner.
No blue shirt could touch the ball home as the cross from Bennett agonisingly flashed across the box just in front of them after 57 minutes.
Referee Toner then took centre stage after 59 minutes when Roberts went to ground under the attentions of Hughes on the edge of the box.
Roberts had earlier been booked for a petulant trip on Elito - and, with the referee judging he’d dived, dismissed the Pompey man in front of an incredulous Fratton End.
Cook stuck with two strikers up front in an effort to get back into the game, despite losing a player.
But things got worse for his side with 21 minutes left when Medy Elito put in a lovely cross from the byline for Boden to head home unopposed.
Then sub Morgan tucked home the third from Mark Byrne’s cross to spark a crowd exodus on a bleak day for Pompey fans.
But there was a nice chance from Blues supporters as they showed solidarity with their manager by singing his name in the game’s death throes.